Concentration Of Active Species Research Articles

Unveiling the Aluminum Doping Effects of In‐Situ Transmogrified Dual‐LDH Heterostructure and Its Fermi‐Level Alignment to Water Splitting Potentials

AbstractThe layered double hydroxide (LDH) captivates the starlight of electrochemical water‐splitting applications due to its stacked layers and larger surface area. A novel approach is reported to integrate CoFe‐LDH/NiAl‐LDH heterostructure through a single‐step in situ transmogrification, harnessing the benefits of LDH. The in situ Raman spectroscopy reveals that aluminum (Al) doping promotes the formation of high‐valent CoIII/IV‐O active species concentration in LDH, whereas without Al dopants, the catalyst predominantly exhibit NiII/III‐O species and underperform the catalytic activity. The projected density of states is very close to the Fermi level positions in Al‐doped samples which significantly enhance the electron transfer processes. The Mott–Schottky studies confirm that both Al40 CoFe30 and Al60 CoFe20 catalysts are p‐type semiconductors, exhibiting a distinct redox behaviors under applied bias. At positive bias, Al60 CoFe20 undergoes downward band bending (accumulation), and align the Fermi‐level near the water oxidation potential, which promotes the oxygen evolution reaction (OER). The negative bias causes upward band bending (deep depletion) in the Al40 CoFe30, and shifts the Fermi‐level near the water reduction potential, and hence facilitates hydrogen evolution reaction (HER). Overall, this study highlights the importance of manipulating Fermi‐level alignment in LDH catalysts through strategic metal doping to achieve targeted water‐splitting reactions.

Kinetics of Oxygen Evolution Reaction in Soluble Lead Flow Batteries

Abstract Kinetics of oxygen evolution reaction (OER) on PbO2 deposited glassy carbon disk electrode in methane sulfonic acid (MSA) is analyzed with cyclic voltammetry and electrochemical impedance spectroscopy, for soluble lead flow battery applications. The effect of concentration of active species (Pb2+), and the electrolyte (MSA) on the OER at the deposited PbO2 layer is investigated. The apparent activation energy of the OER on PbO2, deposited at various overpotential, is obtained from the Arrhenius and Eyring analysis. The apparent activation energy follows a special trend that it increases with overpotential, reaches a maximum and decreases thereafter. This is consistent with the PbO2 specifically deposited from low concentration of MSA (<1M), where the gel layer composed of hydrated PbO(OH)2 is also found. It is observed that low MSA concentration is preferred for limiting the OER at the positive electrode.

Efficacy of neutral electrolyzed water vs. common topical antiseptics in the healing of full‑thickness burn: Preclinical trial in a mouse model.

Burn injuries impose challenges such as infection risk, pain management, fluid loss, electrolyte imbalance and psychological and emotional impact, on healthcare professionals, requiring effective treatments to enhance wound healing. The present study evaluated the efficacy superoxidized electrolyzed solution (SES), with low (SES-low) or high (SES-high) concentrations of active species, alone or in combination with a formulation in gel (G), in comparison with commonly prescribed treatments for burn injury, including nitrofurazone (NF) and silver sulfadiazine (S); normal saline was used as placebo (PI). A scald burn model was established in BALB/c mice. Measurements of the burned area and histological parameters such as inflammatory infiltration state, epithelial regeneration and collagen fibers were evaluated on days 3, 6, 9, 18 and 32 to assess healing score and status. All treatments achieved wound closure at day 32; histopathological parameters indicated that SES-low and SES-low + G performed better than the Pl and S groups (P<0.05). All treatments showed a lower count of inflammatory cells compared with S (P<0.05); for collagen deposition and orientation, SES-low + G showed a more uniform horizontal orientation compared with Pl, SES-high + G, NF and S groups (P<0.05). SES-Low was the most effective substance to induce favorable and organized healing, while S was the worst, inducing disorganized closure of the wound due to a pro-inflammatory effect.

Quantifying concentration distributions in redox flow batteries with neutron radiography

The continued advancement of electrochemical technologies requires an increasingly detailed understanding of the microscopic processes that control their performance, inspiring the development of new multi-modal diagnostic techniques. Here, we introduce a neutron imaging approach to enable the quantification of spatial and temporal variations in species concentrations within an operating redox flow cell. Specifically, we leverage the high attenuation of redox-active organic materials (high hydrogen content) and supporting electrolytes (boron-containing) in solution and perform subtractive neutron imaging of active species and supporting electrolyte. To resolve the concentration profiles across the electrodes, we employ an in-plane imaging configuration and correlate the concentration profiles to cell performance with polarization experiments under different operating conditions. Finally, we use time-of-flight neutron imaging to deconvolute concentrations of active species and supporting electrolyte during operation. Using this approach, we evaluate the influence of cell polarity, voltage bias and flow rate on the concentration distribution within the flow cell and correlate these with the macroscopic performance, thus obtaining an unprecedented level of insight into reactive mass transport. Ultimately, this diagnostic technique can be applied to a range of (electro)chemical technologies and may accelerate the development of new materials and reactor designs.

Hydrothermal tailoring of MnFe2O4 nanospinel integrated with biodegradable polymers for improved CO oxidation efficiency

This study explores the synthesis and characterization of MnFe2O4 nanospinels tailored with biodegradable polymers for enhanced CO oxidation efficiency. MnFe2O4 nanoparticles were prepared using chitosan (CS), CTAB, and cellulose (CE) as stabilizers, followed by hydrothermal aging. Comprehensive characterization using FTIR, XRD, XPS, HRTEM, and TGA revealed that MnFe2O4-CE exhibited the highest surface area (163.2 m²/g), pore volume (0.312 cm³/g), and a high concentration of active oxygen species, particularly lattice oxygen. TEM confirmed the smallest and most uniformly distributed particles in MnFe2O4-CE, averaging 7.5 ± 1.5 nm. These properties contributed to its superior catalytic performance, with effective redox transitions of Mn (Mn2+ to Mn3+) and Fe (Fe3+ to Fe2) enhancing CO oxidation. MnFe2O4-CE demonstrated lower light-off temperatures and maintained high catalytic activity over 13 hours at 150°C, confirming its stability and suitability for industrial applications. This study highlights MnFe2O4-CE's potential as a durable catalyst for environmental remediation, particularly in CO oxidation.

Bioavailability and ecological risk assessment of metal pollutants in ambient PM2.5 in Beijing

Metal pollutants in fine particulate matter (PM2.5) are physiologically toxic, threatening ecosystems through atmospheric deposition. Biotoxicity and bioavailability are mainly determined by the active speciation of metal pollutants in PM2.5. As a megacity in China, Beijing has suffered severe particulate pollution over the past two decades, and the health effects of metal pollutants in PM2.5 have received significant attention. However, there is a limited understanding of the active forms of metals in PM2.5 and their ecological risks to plants, soil or water in Beijing. It is essential that the ecological risks of metal pollutants in PM2.5 are accurately evaluated based on their bioavailability, identifying the key pollutants and revealing historic trends to future risks control. A two-year project measured the chemical speciation of pollution elements (As, Cd, Cu, Cr, Ni, Mn, Pb, Sb, Sr, Ti, and Zn) in PM2.5 in Beijing, in particular their bioavailability, assessing ecological risks and identifying key pollutants. The mass concentrations of total and active species of pollution elements were 199.12 ng/m3 and 114.97 ng/m3, respectively. Active fractions accounted for 57.7 % of the total. Cd had the highest active proportion. Based on the risk assessment code (RAC), most pollution elements except Ti had moderate or high ecological risk, with RAC exceeding 30 %. Cd, with an RAC of 70 %, presented the strongest ecological risk. Comparing our data with previous research shows that concentrations of pollution elements in PM2.5 in Beijing have decreased over the past decade. However, although the total concentrations of Cd in PM2.5 have decreased by >50 % over the past decade, based on machine model simulation, its ecological risk has reduced by only 10 %. Our research shows that the ecological risks of pollution elements remain high despite their decreasing concentrations. Controlling the active species of metal pollutants in PM2.5 in Beijing in the future is vital.

Nonlinear observer for online concentration estimation in vanadium flow batteries based on half-cell voltage measurements

This paper presents a nonlinear observer to estimate the active species concentrations in vanadium flow batteries. To conduct the estimation, the observer relies only on current, flow rate and two half-cell voltage measurements. In contrast to previous works in the field, the proposed observer is capable to deal simultaneously with two significant and challenging conditions: (1) a not necessarily high flow rate, which results in different concentrations for tanks and cells, and (2) presence of crossover and oxidation side reactions, that result in imbalance between the electrolytes on the positive and negative sides of the system. The stability and convergence of the observer are formally demonstrated using a Lyapunov analysis and subsequently validated through comprehensive computer simulations. Finally, utilising the information provided by the observer, a strategy to independently regulate the flow rate of each electrolyte based on their individual state of charge is developed.

High time resolution diagnosis of electron density in helium plasma jets with impurity gas

Atmospheric pressure helium plasma jets are widely used in biomedical applications. Researchers normally introduce small amounts of nitrogen and oxygen (0.2–1.0%) into helium to enhance the electron density and electron energy, thus increasing the concentration of active species in plasma. To further explore why the combination of impurity gases N2/O2 leads to an increase in the electron density from the discharge mechanism, we used a microwave Rayleigh scattering method with excellent time-varying characteristics to monitor the temporal electron density changes when different concentrations of N2/O2 were mixed. The research revealed that even trace amounts of N2/O2 (0.2%) can increase the peak electron density, with this effect being more pronounced when N2 is added, increasing from 3.3 × 1019 to 4.6 × 1019 m−3 in pure helium. As the concentration increases, the introduction of O2 leads to a rapid decrease in the electron density. When 1.0% oxygen is mixed, the electron density decreases from 3.3 × 1019 to 2.4 × 1019 m−3. However, the situation is different when N2 is added, at 0.5% proportion of nitrogen, the electron density increases to its maximum at 6.5 × 1019 m−3. These effects are due to the electronegativity of the oxygen-containing particles or the Penning ionization related to excited nitrogen species.

A double-spiral flow channel of vanadium redox flow batteries for enhancing mass transfer and reducing pressure drop

Flow field optimization is an important approach to enhance the performance of vanadium redox flow batteries, with a focus on improving uniform electrolyte distribution while minimizing pumping losses. In this study, we propose a novel double-spiral flow channel design which differs from the widely-used serpentine and interdigitated flow fields by introducing different flow patterns within VRFB. Two flow fields are achieved by adjusting inlets and outlets positions on the new flow channel, namely, double-spiral flow field with inlets at the center (DSFF(IC)) and double-spiral flow field with outlets at the center (DSFF(OC)). To evaluate the performance of VRFB with the new flow channel, we compare it with other flow channels, including serpentine, interdigitated, and single-spiral flow channels. Bipolar plates with different flow channels are assembled into VRFB single cell for capacity testing, cycling testing, pressure drop testing. Besides, we built a model to visualize VRFBs with different flow channels. The findings demonstrate the superior performance of VRFBs with DSFF(IC) and DSFF(OC). Compared to the serpentine flow channel, the pressure drop caused by the new channel is reduced by 33 % when the flow rate is set at 100 mL/min. Additionally, the charge and discharge tests indicate higher discharge voltage and improved system efficiency in VRFB with double-spiral flow fields. The modeling reveals that DSFF(OC) enhances convective mass transport of the electrolyte within the electrode, improving the concentration and uniformity of active species in the electrode. Impedance spectroscopy and polarization curve tests indicate that DSFF(OC) exhibits lower charge transfer resistance and mass transfer resistance compared to DSFF(IC). Under the same potential, DSFF(OC) demonstrates a higher discharge current density and achieves a peak power density of 321.5 mW/cm2, which is 13.8 % higher than that of DSFF(IC).

Cyclic voltammetry and chronoamperometry: mechanistic tools for organic electrosynthesis.

Electrochemical methods offer unique advantages for chemical synthesis, as the reaction selectivity may be controlled by tuning the applied potential or current. Similarly, measuring the current or potential during the reaction can provide valuable mechanistic insights into these reactions. The aim of this tutorial review is to explain the use of cyclic voltammetry and chronoamperometry to interrogate reaction mechanisms, optimize electrochemical reactions, or design new reactions. Fundamental principles of cyclic voltammetry and chronoamperometry experiments are presented together with the application of these techniques to probe (electro)chemical reactions. Several diagnostic criteria are noted for the use of cyclic voltammetry and chronoamperometry to analyze coupled electrochemical-chemical (EC) reactions, and a series of individual mechanistic studies are presented. Steady state voltammetric and amperometric measurements, using microelectrodes (ME) or rotating disk electrodes (RDE) provide a means to analyze concentrations of redox active species in bulk solution and offer a versatile strategy to conduct kinetic analysis or determine the species present during (electro)synthetic chemical reactions.

Arc-Induced Electrospray Ionization Mass Spectrometry.

Arc-induced electrospray ionization mass spectrometry (AESI-MS) was developed during which alternating current electrospray is simply achieved through the arc plasma. The AESI source exploits the arc's temperature and charge properties to generate aerosols consisting of charged microdroplets. The electrospray region, in which organic molecules are contained within microdroplets, partially overlaps with the arc plasma region. Guided by the electric field, these molecules undergo ionization, yielding ionic target analytes. AESI represents a soft ionization method that combines the mechanisms of atmospheric pressure chemical ionization and electrospray ionization, facilitating the ionization of analytes with wide ranging polarities. The precisely targeted spraying area enhances ion entry into the mass analyzer, thereby enabling excellent ionization efficiency. The AESI source exhibits several notable advantages over the electrospray ionization source, including an elevated but comparable level of active species concentrations and types, simplified mass spectra for direct amino acid analysis, high salt tolerance, versatile analysis of compounds with varying polarities, and reliable quantitative analysis of amino acids in complex matrices. Overall, AESI broadens the methodologies employed to generate microdroplets, providing a technological and scientific framework for creating distinctive electrospray ionization techniques.

Laser Perforated Dual-Scale Porous Electrodes Considering the Interdigitated Flow Field for Vanadium Redox Flow Battery

The conflict between the specific surface area and hydraulic permeability of carbon-based porous electrodes limits the further improvement of redox flow battery (RFB) system performance. Dual-scale electrode design is a feasible approach to overcome this contradiction. In this study, we prepared dual-scale electrodes by perforating graphite felts using an infrared laser. Based on the symmetry of the interdigitated flow field structure, we proposed three dual-scale structure designs with different combinations of large and small pores and tested their performance on a vanadium redox flow battery (VRFB) single cell. The results showed that the design with perforations under the center of the rib could increase the maximum power density by approximately 2.4 times compared to the original electrode. Furthermore, to investigate the effect of the large pores formed by laser perforation on the local electrolyte velocity, active species concentration, and reaction rate distribution, we proposed a pore-network model and investigated the influence of different combinations of large and small pores and different operating conditions on overall performance through numerical simulation. The results showed that the optimal combination of large and small pores is related to the flow rate and other operating conditions, and that setting large pores under the rib near the outlet channel is expected to provide more performance gains in VRFBs equipped with interdigitated flow fields under typical operating flow rates.

Variations of Organic and Inorganic Atmospheric Boundary Layer Gaseous Species by Observations in Moscow and Zvenigorod

Anthropogenic pollution of the atmosphere with organic and inorganic gaseous species has been studied using constant high-quality monitoring of the atmosphere composition both in megacity of Moscow and in its countryside. The article considers continuous measurements of the main climatically and chemically active atmospheric gaseous species concentrations, including volatile organic compounds. The main attention is paid to the comparative analysis, mainly between the megacity and its suburban area, by average species concentrations and some quality features of their seasonal and diurnal variations. The obtained results confirmed the previously studied features of the daily variations of inorganic gaseous species in Moscow and showed such features for organic compounds in the countryside.

Elucidating the role of active oxygen species and hydroxyl groups in the furfural base-free oxidation to furoic acid over δ-MnO2

δ-MnO2 shows potential application in furfural base-free oxidation to furoic acid. While, its catalytic mechanism was unclear, which limited the further improvement of the catalytic activity. Therefore, three δ crystal MnO2 with different hydroxyl and active oxygen species concentrations were prepared and applied in the furfural oxidation reaction. IR, Furfural-IR, O2-TPD, H2O-18O2-TPD, and XPS techniques characterized the hydroxyl and active oxygen species. The results show that the hydroxyl group on δ-MnO2 is important in absorbing and attacking furfural to form geminal diol intermediate. Moreover, two types of oxygen species O-OH and Oads originating from the surface hydroxyl and the strongly adsorbed gas-phase O2, respectively, play an essential role in defhydrogenating geminal diol to furoic acid. Most importantly, the hydroxyl, O-OH, and Oads consumed on δ-MnO2 can be reconstructed under reaction conditions. Among the three δ crystal MnO2, δ-MnO2, with the most abundant hydroxyl and active oxygen species, exhibited the best catalytic performance with 99.53% furfural conversion and nearly 100% furoic acid selectivity. This work identifies the function of hydroxyl and active oxygen species on δ-MnO2 in furfural oxidation reaction, guiding the design of a non-noble metal catalyst for furoic acid synthesis under base-free conditions.

Electrochemical degradation of ciprofloxacin from water: Modeling and prediction using ANN and LSSVM

Ciprofloxacin is a widely used antibiotic that is also a persistent contamination that causes major health and environmental risks. This study investigated the electrochemical removal of ciprofloxacin using a boron-doped diamond anode and a non-supportive electrode to get an accurate understanding of the anode's performance. The effects of current density, initial ciprofloxacin concentration, time, pH, and electrolyte concentration on the removal efficiency of ciprofloxacin were investigated. Additionally, ANN and LSSVM models were used to predict ciprofloxacin removal. The results showed that the BDD anode was effective in removing ciprofloxacin from water, with complete removal of 10 mg L−1 CIP in less than 45 min with electrolyte concentration of 25 g L−1, a current density of 20 mA cm−2, and a pH value of 3. The removal efficiency was found to increase with increasing current density and time because it increases the concentration of active species. The removal efficiency was also found to be higher at acidic pH values and higher electrolyte concentrations. The ANN model was found to be more accurate in predicting ciprofloxacin removal than the LSSVM model, with an R2 of 0.9982 and an AARE% of 2.68%, compared to R2 of 0.9978 and an AARE% of 3.85%. The models were validated using a new set of data, and the results showed that the ANN model was able to accurately predict ciprofloxacin removal under a variety of conditions.

Ammonia Nitrogen Removal by Gas–Liquid Discharge Plasma: Investigating the Voltage Effect and Plasma Action Mechanisms

Atmospheric pressure gas–liquid discharge plasma has garnered considerable attention for its efficacy in wastewater contaminant removal. This study utilized atmospheric oxygen gas–liquid discharge plasma for the treatment of ammonia nitrogen wastewater. The effect of applied voltage on the treatment of ammonia nitrogen wastewater by gas–liquid discharge plasma was discussed, and the potential reaction mechanism was elucidated. As the applied voltage increased from 9 kV to 17 kV, the ammonia nitrogen removal efficiency rose from 49.45% to 99.04%, with an N2 selectivity of 87.72%. The mechanism of ammonia nitrogen degradation by gas–liquid discharge plasma under different applied voltages was deduced through electrical characteristic analysis, emission spectrum diagnosis, and further measurement of the concentration of active species in the gas–liquid two-phase system. The degradation of ammonia nitrogen by gas–liquid discharge plasma primarily relies on the generation of active species in the liquid phase after plasma–gas interactions, rather than direct plasma effects. Increasing the applied voltage leads to changes in discharge morphology, higher energy input, elevated electron excitation temperatures, enhanced collisions, a decrease in plasma electron density, and an increase in rotational temperatures. The change in the plasma state enhances the gas–liquid transfer process and increases the concentration of H2O2, O3, and, ⋅OH in the liquid phase. Ultimately, the efficient removal of ammonia nitrogen from wastewater is achieved.

MOF-derived CoP nanoparticles anchored on P, N co-doped carbon nanoframework as robust electrocatalyst for rechargeable Li-O2 batteries

Currently, transition-metal phosphides (TMPs) coupled with heteroatom-doped carbon materials have attracted promising prospects in lithium‑oxygen (Li-O2) batteries. The CoP electrocatalysts have been extensively studied as popular electrode materials because of their efficient catalytic activity. However, numerous obstacles remain in optimizing synthetic techniques and exploring electrocatalytic mechanisms for CoP-based electrocatalysts. Herein, metal-organic frameworks (MOFs)-derived CoP nanoparticles anchored on P, N co-doped carbon nanoframeworks (CoP@PNCFs) are successfully designed at different phosphorization temperatures. The effects of the concentration of CoP active species, and the amount of P and N doping on the electrochemical performances are comparatively investigated and compared for different catalysts. The optimal catalyst, CoP@PNCF-700, displays high CoP active component, pyridinic-N and graphitic-N content, and abundant defect structures to enhance the electrochemical activity. More importantly, the CoP@PNCF-700 catalytic Li-O2 batteries deliver a high discharge specific capacity of 9630.5 mAh g−1 at 100 mA g−1 and a prominent long cycling stability of 187 cycles with a fixed capacity of 500 mAh g−1 at 200 mA g−1. This effort provides a facile strategy for designing cost-effective electrocatalysts for other energy-storage systems.

Multi-responsive Electropolymer Surface Coatings Based on Azo Molecular Switches and Carbazoles: Light, pH, and Electrochemical Control of Z→E Isomerization in Thin Films.

Light-responsive surfaces are attracting increasing interest, not least because their physicochemical properties can be selectively and temporally controlled by a non-invasive stimulus. Most existing immobilization strategies involve the chemical attachment of light-responsive moieties to the surface, although this approach often suffers from a low surface concentration of active species or a high inhomogeneity of applied coatings. Herein, electropolymerization of carbazoles as a facile and rapid approach for preparing light-responsive azo-based surface coatings is presented. The electrochemical oxidative polymerization of bis-carbazole containing azo-monomers yields stable films, in which the photochemical properties and specific pH sensitivity of azo molecular switches are retained. Moreover, the molecular design enables electrocatalytic control over Z→E azo double bond isomerization facilitated by the conductive polycarbazole backbone. Ultimately, the high degree of control over macromolecular properties yields conductive surface coatings responsive to a range of stimuli, showing great promise as a strategy for versatile application in organic electronics.

Performance of a non-aqueous nanofluid thermally regenerative flow battery for electrical energy recovery from low-grade waste heat

Non-aqueous thermally regenerative battery (non-aqueous TRB) operating at voltages above 1 V is a promising technology for converting low-grade waste heat into electrical energy. To improve the power generation of non-aqueous TRB, the operating parameters that affect the performance of non-aqueous TRB, including the membrane type, electrode materials, acetonitrile volume fraction and electrolyte flow rate were investigated through experimental research. In addition, the thermal-to-electric efficiency of non-aqueous TRB system with different acetonitrile volume fraction and active species concentration was investigated by theoretical calculation. Because of the enhanced active species transport, the optimized maximum power density value of 235 W m−2 was achieved with the use of an anion exchange membrane, reticulated vitreous carbon as the anode electrode, etched carbon felt as the cathode electrode, acetonitrile fraction of 70 %, and electrolyte flow rate of 35 mL min−1. Moreover, theoretical thermal efficiency of 6.6 % was calculated with consisting of 10 % acetonitrile and 0.5 M active species. The above optimized performance in this study is competitive and promotes the development and application of TRBs.

Weakening of springtime Arctic ozone depletion with climate change

Abstract. In the Arctic stratosphere, the combination of chemical ozone depletion by halogenated ozone-depleting substances (hODSs) and dynamic fluctuations can lead to severe ozone minima. These Arctic ozone minima are of great societal concern due to their health and climate impacts. Owing to the success of the Montreal Protocol, hODSs in the stratosphere are gradually declining, resulting in a recovery of the ozone layer. On the other hand, continued greenhouse gas (GHG) emissions cool the stratosphere, possibly enhancing the formation of polar stratospheric clouds (PSCs) and, thus, enabling more efficient chemical ozone destruction. Other processes, such as the acceleration of the Brewer–Dobson circulation, also affect stratospheric temperatures, further complicating the picture. Therefore, it is currently unclear whether major Arctic ozone minima will still occur at the end of the 21st century despite decreasing hODSs. We have examined this question for different emission pathways using simulations conducted within the Chemistry-Climate Model Initiative (CCMI-1 and CCMI-2022) and found large differences in the models' ability to simulate the magnitude of ozone minima in the present-day climate. Models with a generally too-cold polar stratosphere (cold bias) produce pronounced ozone minima under present-day climate conditions because they simulate more PSCs and, thus, high concentrations of active chlorine species (ClOx). These models predict the largest decrease in ozone minima in the future. Conversely, models with a warm polar stratosphere (warm bias) have the smallest sensitivity of ozone minima to future changes in hODS and GHG concentrations. As a result, the scatter among models in terms of the magnitude of Arctic spring ozone minima will decrease in the future. Overall, these results suggest that Arctic ozone minima will become weaker over the next decades, largely due to the decline in hODS abundances. We note that none of the models analysed here project a notable increase of ozone minima in the future. Stratospheric cooling caused by increasing GHG concentrations is expected to play a secondary role as its effect in the Arctic stratosphere is weakened by opposing radiative and dynamical mechanisms.